Waitlist deaths drop under new lung transplant allocation system

Two years ago, the United Network for Organ Sharing implemented new allocation guidelines for lung transplants that prioritize medical urgency. Now new research, published at the 2025 ATS International Conference and in the American Journal of Respiratory and Critical Care Medicine, shows that waitlist outcomes significantly improved under the new system.

Waitlisted patients had a lower risk of death or delisting under the new Composite Allocation Score (CAS) than they did before the guidelines were implemented, researchers said. They also found that the sickest patients on the waitlist saw the largest benefit.

“We always want to make sure that any time we make a change to the allocation system that we’re improving outcomes, especially for our sickest patients,” said first author Mary Raddawi, MD. “This provides confirmation that we’re on the right track.”

Donor lungs were previously allocated based on geographical proximity, with local patients receiving priority access. After a lawsuit in 2017, the allocation radius was expanded to a wider area, and UNOS began working on new guidelines.

Implemented in 2023, the CAS system is based on a compilation of points that prioritizes medical urgency, along with other patient factors.

For the new study, researchers compared outcomes for waitlisted patients before 2017, after the geographic radius was expanded in 2017, and after the CAS was implemented in 2023.

Across the board, they found that 11.2% of patients died or were delisted while waiting for a transplant before 2017. That number declined slightly to 8.4% when the geographical area was extended in 2017 but dropped to 4.1% after CAS.

Improvements were even more dramatic for the patients with the top 5% of waitlist urgency scores. These patients were three times more likely to die on the waitlist before 2017 than they were after the implementation of CAS.

Dr. Raddawi said the results were encouraging, but not surprising. “When you think about the fact that now we’re focusing on many different factors, including medical urgency, it makes sense that the waitlist mortality would go down for our sicker patients—but it is nice to see the actual numbers,” she said.

The findings highlight the importance of providers advocating for their sickest patients and ensuring that their medical urgency is reflected in their scores, she added. “We’re seeing that it really does make a difference for them,” she said.

Researchers plan to follow up on the study by looking at outcomes in greater detail, such as analyzing whether certain biological factors considered in CAS scores are linked to better outcomes among the critically ill.